Pneumatically operated signal trip mechanism



Jan. 9, 1951 F. c. EVANS 5 9 PNEUMATICALLY OPERATED SIGNAL TRIP MECHANISM Original Filed Dec. 16, 1941 4 Sheets-Sheet 1 TO CENTRAL STATION TO OTHER TRANSMITTERS INVENTOR F C EVANS ATTO RN EY Jan. 9, 1951 F, c, EVANS 2,537,185

PNEUMATICALLY OPERATED SIGNAL TRIP MECHANISM Original Filed Dec. 16, 1941 4 Sheets-Sheet 2 w FIG. 3

' INVENTOR F. C EVANS Jan. 9, 1951 c, EVANS 2,537,185

PNEUMATICALLY OPERATED SIGNAL TRIP MECHANISM Original Filed Dec. 16, 1941 4 Sheets-Shgec 5 FIG. 6.

VII 4 55211111? Jan. 9, 1951 F. c. EVANS 5 9 PNEUMATICALLY OPERATED SIGNAL TRIP MECHANISM Original Filed Dec. 16, 1941 4 Sheets-Sheet 4 HNVENTOR F. 0. EVA N 3 BY q ATTORN E! Patented Jan. 9, 1951 PNEUMATICALLY OPERATED SIGNAL TRIP MECHANISM Francis (J. Evans, Dongan Hills, N. Y., assignor to American District Telegraph Company, Jersey City, N. .l'., a corporation of New Jersey Original application December 16, 1941, Serial No.

423,130, now Patent No. 2,410,814, dated November 12, 1947. Divided and this application August 31, 1946, Serial No. 694,385

9 Claims. 1

This invention relates generally to signaling systems and more particularly to aero tube alarm systems for detecting dangerous rises of temperature and initiating an alarm signal in response thereto.

This application is a division of my copending application Serial No. 423,130, filed December 16, 1941, for Signaling System, Patent No. 2,410,- 814, issued November 12, 1947.

Aero tube alarm systems consist of one or more lengths of aero tubing extending through and about an enclosure which it is desired to protect and in such relation to the enclosure that dangerous temperatures can be detected within a minimum time. The tubing may contain a gas either under, at or in excess of atmospheric pressure, which gas expands in response to increases of temperature to thereby increase the pressure within the system. In accordance with conventional practice each end of the tubing circuit is connected to an expansion chamber consisting of a pair of flexible diaphragms for converting changes of pressure within the tubing system into mechanical motion which may be utilized to operate electrical contacts. The tubing system may be operated to respond to a predetermined temperature or a predetermined rate of rise of temperature, the latter characteristic being obtained by the provision of a vent adjacent each expansion chamber for compensating pressure changes occurring at a rate below fixed limits whereby normal temperature changes do not result in the initiation of an alarm. If, however, a dangerous rate of change of temperature occurs, the eX- pansion of the gas within the tubing system occurs at such a high rate that the pressure within the expansion chamber exceeds the limiting pressure to thereby initiate an alarm.

It has been the practice to operate electrical contacts by means of the pressure responsive diaphragms to thereby change the characteristics of an electrical circuit and in turn initiate operation of a signal transmitter by means of an electro-mechanically operated trip mechanism. The

trip mechanism releases an electrical signal transmitting device to cause transmission of code signal impulses from the transmitter located in the protected premises over a transmission line to a central station to thereby summon assistance. The use of electrical circuits including contacts and electro-mechanical devices in the protected premises necessitates the use of local battery sources of electrical energy, thereby in creasing the expense of installation and the amount of investment required in the alarm system.

The alarm signal transmitter, which is electrically tripped, is usually driven by a spring motor which requires manual winding after each alarm transmitting operation, and it is necessary that the condition of the spring driven motor be known to the central station attendant. Therefore, such transmitters are adapted to transmit a restoration signal after each winding operation which signal indicates to the central station attendant that the transmitter has been wound and is in condition to respond to the fire detecting system and transmit an alarm signal. It is necessary, however, to insure that the transmitter is wound to such an extent that the restoration signal will be automatically transmitted as it frequently happens that unskilled persons reset and wind the transmitter, and it is further neces sary that such transmitters be provided with mechanism for preventing a saboteur or incendiary from blocking the action of a transmitter to thereby accomplish his purpose without the initiation of a fire alarm.

The principal object of this invention is to provide a signal transmitter which may be directly and mechanically operated by and in response to small temperature-induced pressure variations in an acre tube system.

A further object of this invention is to provide a mechanically tripped signal transmitter for use in aero tube fire alarm systems which is sensitive to low pressure variations in such systems and at the same time resistant to the effects of vibration.

A further object of this invention is to provide a mechanical trip mechanism in a signal transmitter which is responsive to pressure changes within an aero tubecircuit in a positive and 001- proof manner.

A still further object of this invention is to provide an aero tube fire alarm system including a mechanically tripped signal transmitter, the system having uniform sensitivity to temperature changes of a predetermined rate of rise throughout its entire length.

Still another object of this invention is to provide an aero tube system which may include pressure detecting diaphragms having non-similar characteristics, together with a means for obtaining uniform operation and sensitivity throughout the system in spite of the said nonuniform characteristics.

Further objects and advantages of this system will be apparent after consideration of the following specification and the accompanying drawings wherein:

Fig. 1 diagrammatically illustrates two aero tube fire detecting systems, together with signal transmitters;

Fig. 2 is a front elevation of the signal transmitter embodying this invention;

Fig. 3 is a front of Fig. 2 with the front plate removed;

Fig. 4 is a view from the right side of Fig. 2-;

Fig. 5 is a view from the left side of Fig. 2;

Fig. 6 is an expanded perspective of the transmitter with supporting structure omitted;

Figs. 6a, 6b, and 6c are fragmentary views of a portion of the key winding mechanism shown in Fig. 6;

Fig. 7 illustrates the spring 'rfiotor trip mechanism in it rundown condition;

Fig. 8 illustrates the spring motor trip mecha nism after 120 degrees of rotation during the winding operation;

Fig. 9 illustrates the spring motor trip mechanism after 240 degrees of rotation during the winding operation;

Fig. 10 illustrates the spring motor trip mechanism after 360 degrees of rotation during the winding operation;

Fig. 11 illustrates the spring motor trip mechanism at the start of transmission ofthe restoration signal;

Fig. 12 shows the spring motor trip mechanism in condition to transmit an alarm signal;

Fig. 13 illustrates the diaphragm operated trip mechanism in the running condition; and

Fig. 14 illustrates the diaphragm operated trip mechanism in a position preparatory to transmission of an alarm signal.

Fig. 1 of the drawings illustrates a pair or separate aero tube circuits I and 3, each of which may individually be located within separate enclosures such as one or more rooms in separate buildings or groups of rooms in the same building, for the purpose of detecting dangerous rises of temperature thereinw Each of the circuits l and 3 is'connected to the transmitters 2 and A, respectively, these transmitters being connected as shown in Fig. 1 in a loop circuit which terminates at a central station where annunciators, recorders and alarm devices are arranged to be responsive to transmitted signals. Fig. 1 is an illustration by way of example only, it being intended that the system shall include whatever number of aero tube circuits and transmitters may be necessary and feasible ,in a particular installation.

The tubing circuits terminate at each transmitter in detector units such as are partially shown in Figs. 2 and 3 of the drawings, and which may be constructed in-accordance with the specification and drawings of the patent to F. M. Cowan, No. 2,100,184, 'of November 23, 1937. Fig. 2 of the drawings shows tubing 8 entering the detector unitdesignated in general by numeral 10, this unit containing passages from each end of the tubing to the diaphragm expansion devices i2. Diaphragms 12 are connected together, as shown in Fig. 3 to act either separately or in unison by means of the arm I4 and links !5 so that the operative function of the aero tube system as a whole occurs at the midpoint of arm hi which is the V-shaped'portion It. This overcomes the characteristic of nonuniform response in aero tube systems which'is caused by diflerent degrees'of response, depending upon the .proximityof a fire c'ondition which the actuated end can move.

to one or the other of the diaphragms l2 at the ends of the tube. Thus, the degree of displacement varies in accordance with the proximity of the fire to each diaphragm. However, it will be seen that the degree of movement at the point i6 011 arm [4 will b'e the same regardless of the degree of movement of each of the diaphragms I2. For instance, a fire in the vicinity of the point 5 in tubing circuit I will expand the air within the tubing and cause deflection of diaphragm l2 connected to the near end of the tubing circuit but will cause very slight, if any, deflection of the diaphragm connected to the other end of the tubing circuit. Therefore, one end of the arm 14 will be lowered about the other end of the arm as the pivot point, the point [6 moving one-half the distance through Thus, a fire at either end of the tubing circuit causes a deflection at point 16 equal to one-half the deflection of the actuated diaphragm. If a fire occurs at a point equidistant from the ends of the-loop, both of the diaphragms l2 are deflected only one-half as much as each of them would be if the fire was located close'thereto, but both of the diaphragms are deflected to thereby cause the point 16 of arm I l to move through the same distance as it does when only one diaphragm is deflected.

This characteristic of the system constructed in accordance with this invention eliminates the necessity for adjusting a trip element or contact elements for any particular maxim-um or minimum degree of movement of the diaphragms for the reason that regardless of the-location of the fire with respect to the ends of the loop circuit the point 16 of arm It always travels through the same distance. Furthermore, this feature of the invention averages whatever differences there may be in the characteristics of different diaphragms so that the aerotube circuit is uniformly sensitive throughout its length and the motion of the point [6 of arm I4 is approximately the same regardless of slight variations in the degree of deflection of said different-diaphragms under the same pressureconditions.

The effects of vibration on thetripping mechanism are eliminated by the provision of weight I? in slot 4-! of lever 49. The weight H is adjustable horizontally in slot4'l to vary the downward tension on diaphragms I2 to thereby adjust the point on the performance curves of both of the diaphragms at which they start to deflect in response to pressure impulses from the tubing circuit. The sensitivity of the aero tube circuit is therefore definitely determinable and improved. Weight 51' also deflects .diaphragms I2 to such an extent'that lever 40 is positively retained at its lower limit of travel except when the pressure within the tubing changes this level by. deflecting the diaphragms. Since the position of lever M1 is normally fixed by the effects of weight 11, vibration of the transmitter cannot causeit to'trip, the reason for this being that the right'hand end of the lever 49 must move downwardly totrip the fan 36 but this movement is prevented since diaphragms l2 are normally positioned -by weight 17 to fix the lower limit of travel of this'end of the arm 40. Thus 'theo'nly effects of vibration are tocause upward movement of the right hand end of arm 4t and downwardmovement ofhook 112 which is in fact a' movement in 'the'latchin'g direction with respect to fan36. Therefore, the provision of weight 1 7 overcomes an outstanding 5 defect in mechanically tripped transmitters in that false operation caused by mechanical vibration is completely eliminated.

The system constructed in accordance with this invention is particularly adapted for use in connection with mechanically tripped impulse transmitters such as that shown in Figs. 2 to 14 of the drawings. Fig. 3 of the drawings illustrates in general the source of power for the transmitter together with the trip mechanism which is connected to the point It of arm Hi for releasing the power source upon the occurrence of a predetermined rate-of-rise of temperature within the protected enclosure. The sourc of power in this particular illustration of the impulse transmitter is a spring motor which is most clearly shown in Figs. 4 and 6 of the drawings and comprises a pair of coiled leaf springs 20 and 25 anchored in any suitable fashion to the drive shaft 23 supported in frames i8 and it. Two springs are provided for insuring against the possible loss of a source of power in the event that one spring should fail. The motor drives shafts 2d, 2%, 23 and also supported in frames i8 and 59, through a gear train com-- prising gears 25, 2?, 29, 3| and pinions 32, 33, 3% and 35, whereby the motion of shaft 23 is multiplied to such a speed as to rotate the shaft 3 3 at whatever speed is most suitable. Fan 35 which acts as a governing device and a control device is norm-ally prevented from rotating by means of the lever or detent at} having a hook portion 32 for engagement with a portion of the fan 35. Lever it is pivoted on the adjustable pivots s4 and connected to point it; of arm i i by means of a perpendicular arm 39. The lever to is pivot-ed along its length at such a point that hook 42 moves through a distance equal to the deflection of either of diaphragrns 52 whereby its entire motion is useful at the tripping point.

It is necessary that the degree of engagement between hook 2 and fan 33 be adjustable and, therefore, the pivots '14, supported in the yoke '38, and also lugs t8 extending from yoke 45 are held in alignment vertically in the slots so in frames it? and i9 shown in Fig. 2 of the drawings. The pivots are positioned vertically by an adjustment assembly comprising springs 58, a. screw El and a nut 52 which moves horizontally and engages a lever 5-3 pivotally attached thereto and at its upper end to the yolze 66 whereb r tation of screw i controls the elevation of yoke it together with the degree of engagement between fan 3E and book 32. The yoke 35 is biased downwardly by a pair of springs 56 to provide proper positioning of the entire assembly.

The trip lever if! is arranged to be deflected in a horizontal plane as well as a vertical plane for the purpose of providing a manual release for initiating fire alarms manually. Fan is provided with a slot 3? whereby deflection of lever id in a horizontal direction may break the engagement between hook t2 and fan 35 and allow the mechanism to operate even though the aero tube circuit has not operated. The wide slot 38 in fan 38 permits rotation regardless oi the position of hook 4'2 provided that hool: ii is in alignment with slot 3?. Lever is pivoted for motion in a horizontal plane by means of a pivot member ll extending through the block 45 which is the support for lever 69 pivoted on the pivot screws it. As illustrated, the lever ineludes the bent over portions 43 which engage pivot pin it to allow motion in a horizontal plane as Well a vertical plane. It is to be understood that any suitable pivot arrangement for obtaining motion vertically and horizontally may be used.

The manual trip mechanism includes lever 88 pivoted at 53, as shown in Figs. 2 and 6, and connected with fan 36 by means of aslotted lever E5, the slot 66 therein providing engagement with the lever as to impart horizontal motion thereto. The operating arm 66 is attached to lever E53 and when operated by manual pressure, forces arm 43 through lever 65 to swing the hook %2 into slot 3? of fan 35 to allow the mechanism to operate. Leaf spring 55 acts to force the lever it and consequently hook 32 forwardly to normal fan-locking position.

It is necessary that the manual trip mechanism (and particularl lever (iii) be controlled by the motor winding mechanism to the extent that this lever, after the transmission of alarm signals, remains position causing hool; 42 to be out of the path of fan 35, so that when the springs are rewound and then released to unwind, a restoration signal is automaticaliy transmitted. This operation is desirable since alarm transmitters transmit alarm signals and are then in a run-down condition which requires restoration to the normal condition for again transmitting a subsequent alarm. It is further necessary that the central office attendant be informed or" the fact that the alarm system has been restored to its normal condition, and therefore the hereinbefore described trip mechanism must be controlled during the winding opera tion and. the transmission of restoration signals to start and stop the transmitter at the beginning and end of the restoration signals.

The main shaft 23 of the spring motor has fixed thereon a ratchet wheel id. The pawl ll, which engages with the notches in ratchet wheel it, is pinned on gear 25, as illustrated in the drawings. Gear 25 floats on shaft 23 and is normally locked against rotation as will be explained subsequently, and thus, when the shaft is 1'0 tated by the key, springs 2i and 28 are tightenedv to fully wound condition and held there by pawl "H in engagement with ratchet l8. Shaft 23 also rotates cam member i5 which is fixed thereto. Cam it includes slot 62, the leading edge of which is perpendicular to the vertical surface of the cam so that the pin 6! in lever arm can drop suddenly into slot 62 to thereby provide a positive stopping motion of arm and hook 42 of the tripping mechanisms. The other edge of slot 52 is beveled to lift the pin 5. Secondary earn it floats on shaft 23 and is provided with slot :3 which extends through an arc of several degrees with respect to the center of cam. Pin ll in cam '15 extends through slot l3 and moves freely therein for several degrees of rotation of cam '55 so that there is lost motion be tween earn 175 and the secondary cam Thus, when the shaft 23 rotates through the winding ycle, cams "I i and T5 are also rotated.

Cam 74 supports and moves pin 18 in operative relation with the arm 8% of stop lever 79 which is rotatably pinned to frame l3. Stop lever '59 also includes the projecting lug ill which engages with a pin 82 on wheel 25 to prevent rotation of wheel 25 during the winding cycle. Arm 84 of member 19 engages the manual trip lever Gil to perform the same function as that which occurs when lever 68 is manually operated. Thus, during the winding cycle, lever arm 60 is held in a non-tripping position until pin 78 engages arm to rotate member 19 in a counterclockwise die essence rection; at which time. arm '8l. clisenga'ges':fromf pin;c.82i andiarmf 84 disengages from lever EU.

Lever 19 is held in either of its two positions by spring 83 in engagement with lug 85'. Theoperation of the drive shaft'assembly will be described iIIimOI'E detail later chain the description Transmission of impulses is provided by im pulse" wheel Hi! which rotates with shaft 25;

driven'from gear. 25 throughlpinion 32; Impulse wheel'l f engagesthe'contact springs HI sothat of thetransmission circuit and consequent trans-- mission of the code signals.

The winding mechanism isprovidedwith a key trapping device consisting of a yoke Bil onframe '10 the teeth of wheel I I0 intermittently open springs Hi! to :causedntermittent making and breaking l8 having a keyhole 92Jwhich is so shaped and proportioned that key l 0th the handle "ofwhich i hasibeeni omitted from'the drawing, and the pin g ll of the key 160 can be engaged with slot H32- in hub 16 on'shaft 23 for commencing the windingloperation." The-keyhole i so proportioned, however, that as soon as the winding operation starts, with key lEiU rotated in a clockwise direction, pin ltl rotates behind the yoke 99, which thereby prevents withdrawal of the key fora certain portion of the winding cycle. While thekey canbe rotated counterclockwise :and then repin I0! engages yoke 96 and then the rear sideof member I until rotated to such a point that the transmission of a restoration signal will be I assured. Lever I05 prevents extraction-of the key since it is of such a length that it extends beyond the keyhole in yoke v9i] whereby key E80 must be rotated until clear of the lever. It should be. noticed thatFig. ll of the drawings (wherein thezillustrated parts are similar to those of Fig. 12

in which reference characters'are applied) shows the cam'15' and the associated elements in such a position that pawl ll is out of engagement with ratchet 10 whereby key member I!!! may rotate pastthe end of member I95 at'which time this member is forced back against the cam 15. Pin

I01 may then engage the outer surface of that member so'that, as shaft 23' rotates in a coun- 1 terclockwise direction under the influence of springs: and 2|, key mil-will be forced out of engagement with shaft 23.

Since the drawings illustrate in Figs. 2, 4, 5, 6

and 7 the transmitter in its rundown condition,

the operation will be described starting with the winding operation. When key I90 is inserted in hub. 16 of cam 15, pin It! on the key'en ages in a slot H12- in hub '26. The key is rotated in a clockwise direction through 120 -or--unti=l pawl l on' main gear engages in the first notcnof ratchet was shown inFig. '8. After the paw-l has engaged' the first notch ofa ratchet- 10 -it is possible tO-Withdl'aW the key 109 since it is locked against withdrawalxby virtue of the fact that the pin-:10! has passedunderneath a portion of=' the yoke '90 of'the'keytrapandthus it will be-inece'ssary: to --'CO1'1tinu'6i the clockwise: rotation ot the key andzthe winding'operation before the key cani be removed. ;1.Another-120 of rotation of the key" =.inthe slot 13 in cam'l.

ing more 'tightly *wound. i In the 'meantime ca'r'n 15 is rotated and in so 'doi ng has turned the sec"- ondary cam M by means of pin 11 which engages Therefore secondary cam 74 is n0 onger holding the stop lev 5 the t pped or rundown position but the stop lever still cannot move as springs? is holding it in place by engaging lug .85.

Rotation of the key H10 through another 120 as shown in Fig. 10 causes the notch-62 on cam 15 to pass under pin El in operating arm 6%;- But this pin will be prevented-from falling into the notch by reason of the engagement of arm 84 of stop lever 19 with the end of operating arm 60,

the reason for this arrangement'being'the fact" that the edge of notchfiZ which would contact the pin 6| during the winding operation is vertical as is the surface of the pin that would 'contact the edge. The reason for the vertical edges is to' provide a positive stop by suddenly moving lever 60, arm 65 and hook 42' in engagementwith fan 36, after the transmission of the restoration signal, but if these two vertical surfaces were peryond that point.

tating about its pivot point against spring H36 "-mitted to meet during the winding operation, it would be impossible to wind the mechanism be Considering that the key has"- now been rotated through 360"; it is still impos-- sible to withdraw the key for the reason that the a pin ID! has passed under lever H15, this lever roto permit rotation of th key. his to be noted that lever I05 is long enough to engage a por-" tion of yoke 90 thereby preventing rotation be shown in Fig. 11, before pin 05 becomes disen- 35 -yond the plane of yoke 90, whereby'key see is trapped in its winding position. Therefore the key must be turned through an additional 30 as gaged from lever I05. After 30 return motion lever I05 is beveled at its free end, as illustrated at 10's.

"key lilli may be removed owing to the fact that portion of spring 83 where it'is held as shown in Fig. 11 until forcibly restored to the position shown in Fig. 6. When-stop lever l9 rotates in a 1 counterclockwise direction, arm 84 rises above operatingarm Gilpallowing pin 5| to rest aga nst the surface of cam I5, and the arm 8! of stop .lever 79 is disengaged from pin 82 on gear i5 so that the spring motor is free to drive the mechanism. As the mechanism run after being released in the above manner, ccde wheel I H) is ro tated in the obvious manner through one round of signals which designate the restoration opera tion and cam 15 rotates in a counter-clockwise direction until notch 52 engagespin 6| as shown in Fig. 12, whereupon operating arm 66 moves" about its pivot point 63 under the influence of spring 64, the pin 6| engaging the' vertical sur-'- face of notch 62 in cam 15 to stop the -i echanism. The transmitter is now in its normal or" rest position and ready to be tripped for sending an alarm.

It should be noted that during the return motion of the mechanism, pin Hill of key 5% is' dis engaged from slot I92 owing to the fact'that pin [5| engages the outer'sloping surface of lever" I05 which surface forces the-key free of slot engagesrpawk 'lI with ia--second notch inratchet 102 to thereby preventdefeatof the-transmitter" such as willful application of force through the key to prevent rotation of the mechanism and transmission of an alarm.

The vertical surfaces on pin SI and slot 62 of cam '15 are of particular significance since if these surfaces were round or sloped, the motion of operating lever 53 would be slow and the entire mechanism wouid stop as soon as lever 65 pulled lever 40 to the right far enough to engage a portion of fan 36. This would occur considerably before pin 6| could be fully engaged with slot 62 and under this condition a fire in the protected premises could develop a pressure in the diaphragms l2 and hook 42 would operate satirfactorily, but the first operation of the mechanism would carry arms 60 and 85 further to the right and further into engagement position, and if the pressure did not last sufficiently long or if there was slight rotary motion due to some parts not being in exact alignment, the mechanism might stop because the hook 42 would engage the fan 35. However, the vertical edges on pin 61 and notch 62 permit lever 60 to assume its normal position very rapidly and thus hook 42 is moved into full engagement with fan 35 within one revolution thereof. Consequently when a fire occurs and diaphragms l2 operate, fan 36 is released and with every turn of the mechanism, levers 60 and 65 will move further and further to the left and full disengagement position under the influence of pin BI and arm 60.

The sequence of operations described hereinbefore ends with rotation of code wheel H 9 which occurs as the result of release of the driving motor at the end of the winding cycle. The teeth on code wheel H act on contact springs HI to transmit a one round restoration signal through the central ofiice for the purpose of indicating that the transmitter has been wound and restored to normal condition and is therefore prepared for transmission of an alarm signal.

The aero tube system illustrated by way of example in Fig. 1 normally consists of several circuits, each of which extends through a pro tected area for supervising temperature changes and detecting fire conditions within that area. If a fire should occur near one end of the circuit, pressure in the tubing will increase greatly at that end and very little if at all at the other end, this being due to the well known capillary characteristics of aero tubing which cause transmission of pressure pulses through the tubing. Assuming the above condition, the pressure builds up in the left diaphragm, this particular diaphragm being taken by way of example for purposes of illustration. This diaphragm under the influence of increasing pressure moves down wardly and lowers one end of the crossbar i l, the other diaphragm remaining stationary and serving as a pivot for the operated end of the bar [4. The central portion of crossbar M will descend only one-half as far as the active end of the crossbar for obvious reasons. Thus lever 40 pivots about pivots 44, the end 39 attached to crossbar I t moving downwardly and the op posite end-to which hook 42 is attached moving upwardly. Hock d2 moves a distance equal to the expansion of the diaphragm since that end of arm 4!: is twice as along as the other end. When sufilcient pressure and expansion of diaphragm i2 occurs hook E2 is raised out of engagement with fan 35 thereby allowing the mechanism to start under the influence of the drive springs 25 and 2|. When the mechanism starts, the pin 6| is lifted out of notch 62 in cam 15, thereby rotating operating arm 69 about its pivot 63 so that the notched arm 65 pushes lever 40 to the left whereby the-hook 42 is in linewith the slot in fan 36. Thus if the pressure in the operated diaphragm l2 decreases for some reason, for instance, because of destruction" of a portion of the aero tube circuit by fire, the

mechanism cannot be stopped from running since hook 42 is not only raised about fan 36 but is in alignment with the slot 31.

If the fire occurs in the center of the aero tube circuit, that is, at a point equidistant between its ends, pressure is developed and rises equally throughout the tube circuit so that both diaphragms expand substantially simultaneouslyand at the same rate. Under these circumstances the pressure is distributed between the two -diaphragms and therefore the deflection of eachone is only one-half as great as it would be in the case of a similar fire condition at one end of the circuit. Crossbar I4 is lowered at both ends but only through one-half the distance at each end in comparison to the previously outlined situation where only one diaphragm could expand. Even so, the center of crossbar I4 moves the same distance that it would when the fire is at either end of the circuit, and therefore hook 42 of arm 40 moves through the same distance regardless of the location of the fire with respect to the aero tube'circuit, and thus the center of the circuit is exactly as sensitive to a fire condition as the ends of that circuit. This characteristic of the tripping unit [2, [5, Hi, 39, 40, '52 permits adjustment of the system" to obtain sufficient sensitivity to a fire at the center of the circuit without rendering the system oversensitive to unusual heat conditions which may exist at the ends of the circuit and which determine the extent of sensitivity adjustment. The above described action of cross-arm l4 and lever 50 is the same for fires one-quarter of the way along the circuit or three-quarters of the way along the circuit, or at any other point in the circuit except that both diaphragms will expand a proportional amount and the net movement at the center of the cross-arm l4 will be the same' regardless of the location of the fire with respect to the circuit.

When the transmitter is started, impulse wheel H9 rotates through five complete revolutions, thereby sending a five round signal by operating contact springs I II which are connected to the transmission line. (Jams 74 and i5 rotate counterclockwise from the normal fully wound position shown in Fig. 12 through approximately 330 until pin 18 in cam 54 engages arm on step lever [9, at which time stop lever '19 rotates in a clockwise direction to move the projection to the right of the bent portion of spring 83' and bent arm 8| rotates into the way of pin 82 in main gear 25, thereby stopping the spring motor. At this time cam '55 opens the shunt springs I Hi, since the cutaway portion of the cam allows these springs to open. The transmitter is now in the rundown condition and require winding, as described hereinbefore.

Provision is made for manual operation of the transmitter in that horizontal pressure on lug 68 of arm 63 moves the lever 49 through the slotted link 65 so that hook 42 of arm 40 enters slot 31 and is disengaged from fan 36. Thus the transmitter is again released to operate in the manner described above in connection with initiation of an alarm by the aero tube system. Any form of manually; operated. push :brttori or lever .is suitable for manually initiating analarm but Kg. 4 illustrates byway of example only a break-glass springeoperated rotatable lever at P23, such as thatshown in Patent No. 1,434,096, granted Qctober 31, 1942. When the glass is broken, the spring is released to exert pressure on arm 58 of lever 68, whereupon pin 6| is forced-out of the slot 52 after which further pressure is unnecessary sinceoperating arm 60 .is maintained in the operated position byi'the surface of cam 15'pressing'on pin 6 I.

The release mechanism shown in Figs. 4, and ii isadjustable by-meansof thescrew 5i which-when rota-ted,- forces the nut 52 in a horizontal direction thereby lifting .the yoke it through link 5301 lowering it, depending upon thedirection of rotation-of screw 5!.- Clockwise rotation of screwl:raises,yoke fito decrease the pressure required to release the .mechanism, since the end-of lever arm iii is also raised. Rotation of the screw in the opposite direction lowers yoke 46 and thereby. increases the pressure necessary to' effect release of the, mechanism.

vThe two contacts mounted on the'sarne support as the spring 54 are utilized for the purpose of actuating local .alarmqor' for any other desired purpose such as activating relays controlling a power source and the like whenthe transmitter isa-opera-te'd to transmit a signal. By reference toFig..6.it .wlllbeseen that the outermost long contact ofthis pair hasa. spacer engaging the upper :end of the spring iid and when. this. spring 64' isinits: most forward positiomthe contacts are heldop'en. However,- when springM is moved toitherear by movementof .lever 69, theouter long: contact of the pair. follows such movement closing. the two contact-points and thereby permitting the closing ofsuch local'circuit as may be,,provided. "The two contacts Ht are used in the vnormal'manru er to 51101101117121.113 other trans mitter following this particular transmitter in the. customary loop circuit so-that such later transmitter cannot. operate during the running o'f-this transmitter.

. Itis to .be noted that the 'aero tube. system has increased sensitivity- -because the diaphragms are stressed a;predetermined amount by means of the weight I! whereby a downward force is exe'rted-onthe end'ofarmat which is attached tothecross-arm 'i 4. Theweight provides a fairly heavy gravitational forcetoperform the actual workcof operating the detent when the adia phragms are expanded whereby instead ofrelyingentirely uponthe aero tube pressure and the diaphragm as the sole source of power, they merely permit the gravitational force exerted by weight I? to take effect on arm 28 as the pres sure increases in the-aero tubingcircuit. Weight lT-also loads or biases the diap-hragms I2 so that they actuallystart operating.- at a point on the straight l'ne portion of their expansion curves so thattheir action is more accurately predictable-and greater movement per ounce of pressure increase is obtained. A further important advantage of. the function of..weight I l is the fact that lever arm it is loaded inthe. direction in wh'ch it. operates, and it isfree tomovefn. the holding direction whereby vibration does not causeaccidental release, change'of adjustment, or jamming of. the mechanism. .Th's feature of the invention makes a mechanically tripped transmitter practical. andfool-proof. Furthermore, a series of releases by vibration would have to occur before the transmitter. could be accidentally tripped I 12 since," as is plainly evident, the .fan .36 must. go througha number :of revolutions beforecar'n-TE can have moved sufficiently to d'sengage pinyfil from slot- 62 to efiect actual' completereleaserof the mechanism.

From the above description it is also'evident that another important feature of this invention is the arrangement of the cross-arm M for providing a tripping motion which is always uniform in length regardless of the location of the fire with respect to the ends of the aerotube circuit, whereby equal sensit vity of all .parts'ofthe. circuit is obtained.

A still further important feature'oi this invention is the provision of the key-trapping mechanismincluding yoke=9il and arm I which not onlytrapsthe key inits operating position until the transmitting mechanism is fully wound :but also forces the key iii!) out ofengagement with the driving mechanism as the restoration, signal is being transmitted. This featureof the invention makes it possible for the station operator to detec-tthe' stoppage of the mechanism duringa restoration signal and prevents attempts to do.- feat the mechanism by applyingforce through the key at the time an alarm condition exists, as it is obvious that the key cannot engagethe driving mechanism once the mechanism is in its normal fully wound condition. Furthermore, the key trapping mechanism simplifies the winding operation in that it compels a certain definite sequence of operations and only those operations whereby an amateur can wind the transmitter.

Another advantage derived from this inven-- Itis not intended that the. tripping mechanismoperated by the aero tube'system shall be limited only tense in signal transmitters as it equally adaptable foruse in connection with-automatically operated valves in fire extinguishing sprinklersystems where such valves areof the type adapted to be opened by a tripping mechanism. It isalso intended that this mechanism embodying the invention disclosed herein may be adapt-- able to trip any form of device wherein a trip mechanism is useful and necessary. Further advantages and modifications of this invention will be apparent to those skilled in the art, and

therefore it is desired that this invention not be limited to the specific mechanical elements shown herein but only as required by the prior art and the appended claims. The winding mechanism described and illustrated. herein constitutes .the subjectmatter of my copending divisional application Serial No. 458,509, filed August 4, 1942 Patent No. 2.34131 granted March 1%,.1941.

.What .is claimed. is:

1. In combination, an acre tube fire detecting system for supervising dangerous temperature changes within a protected area, said system including pressure responsive diaphragms at each end thereof,"sa id diaph-rag'ms being independent 1y responsive to pressure changes in said system, a non-rigid mechanical connection directly between said diaphragms, tripping lever pivoted for motion for exercising a control function, a link connecting said mechanical connection between the diaphragms with said lever and a weight associated with said lever in such relation thereto that a predetermined bias is exerted through the link and connection on said diaphragms, said diaphragms being free to expand without exerting force on said connection and said link.

2. In combination, a pneumatic tube system, said system including pressure responsive diaphragms at each end thereof, said diaphragms being independently responsive to pressure changes in said system, a non-rigid connection directly between said diaphragms, a tripping lever pivoted for control-exercising motion, a link connecting said connection between the diaphragms with said lever and means for exerting predetermined bias on said diaphragms, said diaphragms being free to expand without exerting force on said connection and said link.

3. In combination, an aero tube fire detecting system for supervising dangerous temperature changes within a protected area, said system including pressure responsive diaphragms at each end thereof, said diaphragms being independently responsive to pressure changes in said system, a non-rigid mechanical connection directly between said diaphragms, a tripping lever pivoted for motion in a tripping direction for exercising a control function, and a link connecting the midpoint of said mechanical connection with said lever, said diaphragms being free to expand without exerting force on said connection and said link.

4. In combination a pneumatic tube system,

said system including pressure responsive devices 5. In combination, an aero tube system for detecting dangerous temperature changes within a protected area and including a pressure responsive device at each end of said system, said devices being independently responsive to pressure changes in said system, a non-rigid mechanical tripping mechanism for accomplishing a control function, a mechanical connection directly between said devices, a link connected midway of said connection and to said tripping mechanism, and means associated with said tripping mechanism for exerting a biasing force on said devices, said devices being free to expand without exerting force on said connection and said link.

6. In combination, an aero tube system for detecting dangerous temperature changes within a protected area and including a, pressure responsive device at each end of said system, said devices being independently responsive to pressure changes in said system, a non-rigid mechanical tripping mechanism for accomplishing a control function, and means associated with said tripping mechanism for exerting a biasing force on said devices, said devices being free to expand without exerting force on said tripping mechanism.

7. In combination, a pneumatic tube system for detecting temperature changes within a protected area and including a pressure responsive device at each end of said system, said devices being independently responsive to pressure changes in said system, a mechanical tripping device for accomplishing a control function, a non-rigid mechanical connection directly between said devices and a link connected midway of said connection and to said tripping mechanism, said devices being free to expand without exerting force on said connection and said link.

8. In combination, an aero tube fire detecting system of the character described including a pressure-responsive diaphragm arranged to be affected by variations of pressure in the tubing, releasing mechanism for exercising control functions, a non-rigid link so connecting said release mechanism and said diaphragm that said diaphragm can expand without exerting force on said link, and a weight associated with said link and arranged to exert a predetermined bias on said diaphragm and to operate said releasing mechanism only upon predetermined expansion of said diaphragm.

9. In combination, an aero tube fire detecting system of the character described including a pressure-responsive diaphragm arranged to be affected by variations of pressure in the tubing, releasing mechanism for exercising controlling functions and a non-rigid weighted connection between said diaphragm and said release mechanism movable to render the releasing mechanism effective only upon predetermined operative defiection of the diaphragm and movable only in the opposite direction by vibration to insure against release of the mechanism when the mechanism is subjected to vibration, said diaphragm being free to expand without exerting force on said connection.

FRANCIS C. EVANS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 963,039 Farquhar July 5, 1910 969,414 Shepherd Sept. 6, 1910 1,603,072 Denzler Oct. 12, 1926 1,938,845 Lowe Dec. 12, 1933 1,973,535 Lowe Nov. 11, 1934 2,275,949 Evans Mar. 10, 1942 FOREIGN PATENTS Number Country Date 17,665 Australia July 30, 1929 

